Conventional buckles for swimming fins include, for example, two parts: a first part connected to a side of the shoe and a second part joined to a strap, the first and second parts being in snap engagement with one another. While useful, buckles of this type have been found disadvantageous in that they must necessarily be loosened to enable the fin to be put on the user's foot, and require adjustment of strap tension each time the fin is put on.
A buckle for swimming fins that can be opened without separating it into two separate parts is described in European patent no. 687484 that is inspired by prior solutions already in use in the field of sports equipment. According to this patent the part of the buckle integral with the side of the shoe and the part attached to the end of the strap are articulated to each other via a connection lever that allows the buckle part connected to the strap to be moved from a position of attachment on the buckle part connected to the side of the shoe, at which the strap tightens the foot of the user at the rear, to a position of disengagement wherein the buckle part whereto the strap is attached is moved backwards in relation to the fixed part, eliminating the tension of the strap and thus allowing the user to put the fin on or take it off. With this system it is not possible to separate the parts that make up the buckle, and therefore it is not possible to separate the strap from the fin. Consequently, a first disadvantage of this known device consists in that the user, in order to take the fin off, albeit with the strap loosened, must always remove it from the foot: i.e. it is necessary to make the loosened strap pass behind the heel, with the aid if necessary, of his/her hand, which may delay the operation in emergency conditions.
In the buckle described in the aforementioned European patent the buckle part connected to the strap is attached to the buckle part integral with the shoe by means of a snap connection, both during the opening phase and the closure phase, between the intermediate articulation lever and a pair of side flanges rising up from the buckle part integral with the shoe. In order to open the buckle the user has to push the free end of the lever outwards.
A second disadvantage of this device consists in that such a closure system is not totally safe, in that the opening movement may also be caused accidentally in the case of impact or in the case wherein the free end of the lever tangles in some external projection.
A third disadvantage of this device consists in that, after having worn the fin and closed the buckle, the tension of the strap can be increased but not decreased. With the fin on, the strap provides a tight length adhering to the foot and a free end which can be grasped and pulled to increase the tension of the strap. In order to loosen the tension a few fingers have to be inserted between the foot of the user and the tight strap, which is anything but easy. Therefore, in order to loosen a strap which, once worn, would appear too tight, the strap has to be opened and the adjustment operation repeated.